In automotive and other industrial applications, special sensors are used to determine shaft speed and angular position, for example, as well as linear motion sensing. Generally, such sensors are either of the variable reluctance variety or comprise a toothed steel wheel (i.e., exciter) spaced from a sensor comprising a magnet and a magnetoresistor or a Hall effect device. Other types of sensors require multi-bit digital encoding for position sensing and other uses.
A permanent magnet with an appropriate magnetization pattern can serve as the exciter component of a magnetoresistive sensor without the need for a separate bias magnet. However, by conventional production methods currently in use, very small magnetic exciters could not be magnetized with a pattern providing the necessary combination of resolution and field strength and the cost of a large permanent magnet exciter would be prohibitive. If several different magnetization patterns were desired side-by-side, such as for multi-digital encoding, more complex manufacturing problems arise; either machining or magnetizing such an exciter as one unit is very costly and is seldom done.